Heretofore, polyfunctional compounds having a double bond have been used for many uses, for example, as a starting material or the like of polymerizable compositions.
These polymerizable compositions are cured predominantly by radical polymerization under light or heat. In particular, a high-speed photopolymerization by an ultraviolet ray (UV) is recently employed from the standpoint of profitability. The polymerizable composition used for the high-speed photopolymerization is generally an acrylic compound or an unsaturated carboxylic acid ester-type compound. However, these compounds have the following problems.
The acrylic compound as a crosslinked monomer can be cured within a relatively short time in UV curing and therefore, is applied to various UV curing materials such as coating material and coating, however, this monomer has a problem in that the skin irritation is relatively high and since the compound is prone to curing inhibition by oxygen, stickiness is readily generated at the formation of a thin film.
With respect to the unsaturated carboxylic acid ester-type compound, dialkyl esters of fumaric acid or maleic acid are known, however, these compounds are individually poor in the radical polymerization property and even when copolymerized with another resin, the degree of crosslinking is not sufficiently high and the cured product obtained may suffer from insufficient strength in some cases. Furthermore, the unsaturated polyester by itself has a large molecular weight and is poor in the homopolymerizability, therefore, a styrene monomer is generally used as a reactive diluent. However, in view of workability such as odor, an alternative of the styrene monomer is demanded.
In order to overcome these problems, vinyl ethers as one of alkenyl ethers are recently taken notice of as a non-acrylic compound.
The vinyl ethers are generally used as a curable material for cationic polymerization system. It is said that radical polymerization of the vinyl ether itself scarcely proceeds when used alone, however, a report in Rad. Tech. North America, 167 (1992) states that copolymerization proceeds between maleate and vinyl ether.
Other than this, some examples of copolymerization systems are also known. U.S. Pat. Nos. 5,334,455 and 5,334,456 describe a system where a polyfunctional vinyl ether is polymerized with a reactant between epoxy and maleic anhydride and a system where a polyfunctional vinyl ether is polymerized with a maleate, and Japanese Patent 2,705,916 describes a composition of an unsaturated polyester and a vinyl ether.
In addition, the vinyl ether is known to copolymerize with an acrylate despite its low copolymerizability.
The vinyl ether is characterized by low viscosity, excellent diluting ability and high adhesion to a substrate at the curing but, as described above, exhibits poor radical polymerizability when used alone. Therefore, in the system where an unsaturated polyester or the like is blended, the vinyl ether group is incompletely polymerized to fail in bringing out the physical properties of the cured product and furthermore, the ratio of the other polymerizable group to the vinyl ether group in the polymerization must be adjusted, giving rise to a problem that the amount of vinyl ether used is limited.
In order to overcome these problems, (the term “JP-B” as used herein means an “examined Japanese patent publication”) describes a method for producing a compound having a vinyl ether group at the terminal and having a maleate structure in the inside, and British Patent 1,188,112 describes a compound having an allyl ether group at the terminal and having a maleate or fumarate structure in the inside.
These polymerizable compounds have, however, only two polymerizable groups at the terminal and one polymerizable group in the inside and still cannot have a sufficiently large number of crosslinking points.
The object of the present invention is to provide a novel fumarate derivative which can overcome the problems in conventional radical polymerizable compounds, such as curing inhibition by oxygen at curing or low surface hardness of the cured product, and which has a sufficiently large number of crosslinking points. The object of the present invention includes providing a method for producing the derivative, a polymerizable composition containing the derivative, and a cured product thereof.